FORM OF CONVERTIBLE DEBENTURE


"THESE  SECURITIES HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS
AMENDED (THE  "SECURITIES  ACT"), OR THE SECURITIES  LAWS OF ANY STATE,  AND ARE
BEING  OFFERED  AND  SOLD  PURSUANT  TO  AN  EXEMPTION  FROM  THE   REGISTRATION
REQUIREMENTS  OF THE SECURITIES ACT AND SUCH LAWS.  THESE  SECURITIES MAY NOT BE
SOLD OR TRANSFERRED EXCEPT PURSUANT TO AN EFFECTIVE REGISTRATION STATEMENT UNDER
THE SECURITIES ACT OR PURSUANT TO AN AVAILABLE  EXEMPTION FROM THE  REGISTRATION
REQUIREMENTS OF THE SECURITIES ACT OR SUCH OTHER LAWS."


                            4% CONVERTIBLE DEBENTURE
                               Due March 31, 1999

March __, 1997
$2,510,000

No. ESI-1A

     Earth  Sciences,  Inc., a Colorado  corporation  with  principal  executive
offices located at 910 12th Street, Golden, Colorado 80101 the ("Company"),  for
value  received,  hereby  promises to pay to the Holder (as defined  below),  or
order, on March 31, 1999 (the "Maturity  Date") the principal sum of Two Million
Five Hundred and Ten Thousand  Dollars and No Cents  ($2,510,000.00)  and to pay
interest thereon from the date of original issuance (or the most recent interest
payment  date to which  interest has been paid),  quarterly in arrears,  on each
March 31, June 30, September 30 and December 31 of each year, commencing on June
30, 1997, at the rate of 4% per annum (the "Debenture Interest Rate"), until the
principal  of this  Debenture  has  been  paid in full or duly  and  irrevocably
provided  for. The interest so payable and duly and  punctually  provided for on
any  interest  payment  date  shall be paid to the  Person  in whose  name  this
Debenture is registered at the close of business on the 15th day next  preceding
the applicable  interest  payment date and all interest payable on the principal
amount of this  Debenture  shall be  calculated on the basis of 365-day year for
the actual number of days elapsed.

                                    ARTICLE 1
                                   DEFINITIONS

     SECTION 1.1 Definitions. The terms defined in this Article whenever used in
this Debenture have the following respective meanings:

          (a)  "Additional  Capital Shares" has the meaning set forth in Section
3.1(c).

                                                   

<PAGE>

          (b)  "Affiliate"  has the meaning  ascribed to such term in Rule 12b-2
under the Securities Exchange Act of 1934, as amended.

          (c) "Business Day" means a day other than Saturday,  Sunday or any day
on which banks  located in the state of New York are  authorized or obligated to
close.

          (d) "Capital  Shares"  means the Common Shares and any other shares of
any other class or series of common stock,  whether now or hereafter  authorized
and however designated,  which have the right to participate in the distribution
of earnings and assets (upon  dissolution,  liquidation  or  winding-up)  of the
Company.

          (e) "Closing Date" means March __, 1997.

          (f)  "Common  Shares" or  "Common  Stock"  means  shares of the common
stock, $.01 par value, of the Company.

          (g) "Common Stock Issued at  Conversion"  when used with  reference to
the  securities  issuable upon  conversion of this  Debenture,  means all Common
Shares now or hereafter  Outstanding and securities of any other class or series
into  which the  Debenture  hereafter  shall have been  changed or  substituted,
whether now or hereafter created and however designated.

          (h) "Company" means Earth Sciences, Inc., a Colorado corporation,  and
any successor or resulting corporation by way of merger, consolidation,  sale or
exchange of all or substantially all of the Company's assets, or otherwise.

          (i) "Conversion Date" means any day on which all or any portion of the
principal  amount  of  this  Debenture  is  converted  in  accordance  with  the
provisions hereof.

          (j) "Conversion Notice" has the meaning set forth in Section 3.2.

          (k) "Conversion Price" has the meaning set forth in Section 3.1.

          (l) "Conversion Ratio" has the meaning set forth in Section 3.1.

          (m)  "Current  Market  Price" on any date of  determination  means the
closing  bid price of a Common  Share on such day as  reported  on the  National
Association of Securities  Dealers,  Inc. Automated  Quotation  ("NASDAQ") Small
Market System or, if the Common Shares are listed on the NASDAQ  National Market
Capitalization  System  or  on  an  established  United  States  national  stock


                                        2

<PAGE>

exchange, the  closing  price of a Common  Share on such day as reported by such
system or exchange (provided,  that the NASDAQ quotation shall shall be utilized
in the event of the dual listing of the Common Shares).

          (n) "Debenture" means this 4% Convertible Debenture due March 31, 1999
of the Company or such other  convertible  debentures  or  Debentures  exchanged
therefor as provided in Section 2.1.

          (o) "Default  Interest Rate" shall be equal to the Debenture  Interest
Rate plus an additional 4% per annum.

          (p) "Event of Default" has the meaning set forth in Section 6.1.

          (q) "Holder" means ___________________,  any successor thereto, or any
Person to whom this Debenture is subsequently transferred in accordance with the
provisions hereof.

          (r)  "Market  Disruption  Event"  means any event  that  results  in a
material suspension or limitation of trading of Common Shares on NASDAQ.

          (s) "Market  Price" per Common  Share means the average of the closing
bid  prices  of the  Common  Shares  as  reported  on the  NASDAQ  Small  Market
Capitalization  System for the five Trading Days in any Valuation  Period or, if
the  Common  Shares are listed on the  NASDAQ  National  Market  System or on an
established  United States national stock  exchange,  the average of the closing
prices of the Common Shares for the five Trading Days in any Valuation Period as
reported by such system or exchange  (provided,  that the NASDAQ quotation shall
shall be utilized in the event of the dual listing of the Common Shares).

          (t) "Maximum Rate" has the meaning set forth in Section 6.3.

          (u) "Outstanding" when used with reference to Common Shares or Capital
Shares (collectively, "Shares"), means, on any date of determination, all issued
and  outstanding  Shares,  and includes  all such Shares  issuable in respect of
outstanding scrip or any certificates  representing fractional interests in such
Shares; provided,  however, that any such Shares directly or indirectly owned or
held by or for the account of the Company or any Subsidiary of the Company shall
not be deemed "Outstanding" for purposes hereof.


                                        3

<PAGE>

          (v) "Person" means an individual,  a  corporation,  a partnership,  an
association,   a  limited   liability   company,   a   unincorporated   business
organization,  a trust or other entity or  organization,  and any  government or
political subdivision or any agency or instrumentality thereof.

          (w) "Registration  Rights  Agreement" means that certain  registration
rights   agreement   dated   March   __,   1997,   between   the   Company   and
________________________.

          (x) "SEC" means the United States Securities and Exchange Commission.

          (y) "Securities Act" means the Securities Act of 1933, as amended, and
the rules and regulations of the SEC thereunder, all as in effect at the time.

          (z)  "Securities  Purchase  Agreement"  means that certain  Securities
Purchase   Agreement   dated   March  __,   1997,   between   the   Company  and
___________________________.


          (aa)  "Subsidiary"  means  any  entity  of which  securities  or other
ownership  interests  having  ordinary  voting  power to elect a majority of the
board of directors  or other  persons  performing  similar  functions  are owned
directly or indirectly by the Company.

          (bb)  "Trading  Day"  means  any day on which  purchases  and sales of
securities  authorized  for quotation on the NASDAQ Small Market  Capitalization
System  are  reported  thereon  and on  which no  Market  Disruption  Event  has
occurred.

          (cc) "Valuation Event" has the meaning set forth in Section 3.1.

          (dd) "Valuation  Period" means the five Trading Day period immediately
preceding the Conversion Date.

          All  references  to "cash" or "$" herein means  currency of the United
States of America.

                                    ARTICLE 2
                             EXCHANGES AND TRANSFER

     SECTION 2.1 Exchange and Registration of Transfer of Debentures. The Holder
may, at its option,  surrender this Debenture at the principal executive offices
of the Company and receive in exchange therefor a Debenture or Debentures,  each
in the  denomination  of  $10,000  or  integral  multiples  of  $1,000 in excess
thereof,  dated as of the date of this Debenture,  and,  subject to Section 4.2,
payable to such Person or order as may be designated by such Holder. The

                                        4

<PAGE>

aggregate  principal  amount  of  the  Debenture  or  Debentures   exchanged  in
accordance  with this  Section 2.1 shall equal the  aggregate  unpaid  principal
amount of this Debenture as of the date of such  surrender;  provided,  however,
that upon any  exchange  pursuant to this  Section 2.1 there shall be filed with
the  Company  the name and  address  for all  purposes  hereof of the  Holder or
Holders  of the  Debenture  or  Debentures  delivered  in  such  exchange.  This
Debenture,  when  presented  for  registration  of transfer  or for  exchange or
conversion,  shall (if so  required  by the  Company)  be duly  endorsed,  or be
accompanied by a written instrument of transfer in form reasonably  satisfactory
to the Company duly executed, by the Holder duly authorized in writing.


     SECTION 2.2 Loss, Theft, Destruction of Debenture. Upon receipt of evidence
satisfactory  to the Company of the loss,  theft,  destruction  or mutilation of
this Debenture  and, in the case of any such loss,  theft or  destruction,  upon
receipt of indemnity or security reasonably  satisfactory to the Company, or, in
the  case of any  such  mutilation,  upon  surrender  and  cancellation  of this
Debenture,  the Company  shall make,  issue and  deliver,  in lieu of such lost,
stolen,  destroyed or  mutilated  Debenture,  a new  Debenture of like tenor and
unpaid  principal  amount dated as of the date hereof.  This Debenture  shall be
held and owned upon the express  condition  that the  provisions of this Section
2.2 are exclusive  with respect to the  replacement  of a mutilated,  destroyed,
lost or  stolen  Debenture  and shall  preclude  any and all  other  rights  and
remedies notwithstanding any law or statute existing or hereafter enacted to the
contrary  with respect to the  replacement  of negotiable  instruments  or other
securities without the surrender thereof.

     SECTION 2.3 Who Deemed Absolute  Owner.  The Company may deem the Person in
whose name this  Debenture  shall be registered  upon the registry  books of the
Company  to be,  and may  treat it as,  the  absolute  owner  of this  Debenture
(whether or not this  Debenture  shall be overdue)  for the purpose of receiving
payment of or on  account of the  principal  amount of this  Debenture,  for the
conversion of this Debenture and for all other  purposes,  and the Company shall
not be  affected  by any  notice to the  contrary.  All such  payments  and such
conversion  shall be valid and  effectual to satisfy and discharge the liability
upon this  Debenture to the extent of the sum or sums so paid or the  conversion
so made.



                                        5

<PAGE>

                                    Article 3
                             CONVERSION OF DEBENTURE

     SECTION 3.1 Conversion;  Conversion  Price. At the option of the Holder, at
any time, and from time to time,  from and after the 45th day following the date
of issuance of this Debenture  until this Debenture is paid in full at maturity,
this  Debenture  may be  converted,  either in whole or in part,  up to the full
principal  amount  hereof  (in  increments  of not less than  $10,000  principal
amount) into Common Shares (calculated as to each such conversion to the nearest
1/100th of a share), at a conversion price (the "Conversion Price") equal to 75%
of the  Market  Price  (the  "Conversion  Ratio"),  but in no  event  shall  the
Conversion  Price be in excess of $_______ per Common Share (the Current  Market
Price on the day preceding the execution by the Buyer of the Securities Purchase
Agreement);  provided,  however,  that the  Holder  shall  not have the right to
convert any  portion of this  Debenture  to the extent that the  issuance to the
Holder of Common  Shares upon such  conversion  would result in the Holder being
deemed  the  "beneficial  owner"  of 5% or more of the then  outstanding  Common
Shares within the meaning of Rule 13d-3 of the Securities  Exchange Act of 1934,
as amended.  At the Company's option,  the amount of accrued and unpaid interest
as of the Conversion  Date shall not be subject to conversion but instead may be
paid in cash as of the Conversion Date.

          Notwithstanding  anything  to  the  contrary  contained  herein,  if a
Valuation Event occurs during any Valuation Period, a new Valuation Period shall
begin on the Trading Day immediately  following the occurrence of such Valuation
Event and end on the Conversion Date;  provided that if a Valuation Event occurs
on the fifth day of any Valuation Period, then the Conversion Price shall be the
Current  Market Price of the Common Shares on such day; and  provided,  further,
that the Holder may,  in its  discretion,  postpone  such  Conversion  Date to a
Trading Day which is no more than five Trading Days after the  occurrence of the
latest  Valuation Event. In the event that the Holder deems the Valuation Period
to be other than the five Trading Days immediately prior to the Conversion Date,
the Holder shall give written  notice of such fact to the Company at the time of
conversion.

For purposes of this  Section  3.1, a  "Valuation  Event" shall mean an event in
which  the  Company  at any time  during a  Valuation  Period  takes  any of the
following actions:

          (a) subdivides or combines its Capital Shares;

          (b)  pays  a  dividend  in its  Capital  Shares  or  makes  any  other
distribution of its Capital Shares;


                                        6

<PAGE>

          (c) issues any  additional  Capital  Shares (the  "Additional  Capital
Shares"), otherwise than as provided in the foregoing Sections 3.1(a) and 3.1(b)
above,  at a price per share less, or for other  consideration  lower,  than the
Current Market Price in effect  immediately prior to such issuances,  or without
consideration, except for issuances under employee benefit plans consistent with
those presently in effect and issuances under  presently  outstanding  warrants,
options or convertible securities;

          (d) issues any  warrants,  options or other rights to subscribe for or
purchase  any  Additional  Capital  Shares  and the  price  per  share for which
Additional  Capital  Shares may at any time  thereafter be issuable  pursuant to
such  warrants,  options or other rights  shall be less than the Current  Market
Price in effect immediately prior to such issuance;

          (e)  issues  any  securities   convertible  into  or  exchangeable  or
exercisable  for  Capital  Shares  and the  consideration  per  share  for which
Additional Capital Shares may at any time thereafter be issuable pursuant to the
terms of such convertible,  exchangeable or exercisable securities shall be less
than the Current Market Price in effect immediately prior to such issuance;

          (f) makes a distribution of its assets or evidences of indebtedness to
the holders of its  Capital  Shares as a dividend  in  liquidation  or by way of
return of capital or other than as a dividend payable out of earnings or surplus
legally  available  for the payment of  dividends  under  applicable  law or any
distribution to such holders made in respect of the sale of all or substantially
all of the Company's assets (other than under the circumstances  provided for in
the foregoing Sections 3.1(a) through 3.1(e)), provided, in each case, that such
distribution  described in this Section  3.1(f) does not  constitute an Event of
Default; or

          (g) takes any  action  affecting  the  number of  Outstanding  Capital
Shares,  other than an action described in any of the foregoing  Sections 3.1(a)
through 3.1(f) hereof, inclusive, which in the opinion of the Company's Board of
Directors,  determined in good faith,  would have a material adverse effect upon
the rights of the Holder at the time of a conversion of this Debenture.

     SECTION 3.2  Exercise  of  Conversion  Privilege.  (a)  Conversion  of this
Debenture may be exercised, in whole or in part, by the Holder by telecopying an
executed and completed  notice of conversion in the form annexed hereto as Annex
I (the  "Conversion  Notice")  to the  Company  and  sending a  manually  signed
original  Conversion Notice and this Debenture to the Company by express courier


                                        7

<PAGE>

not later  than five (5)  Business  Days  next  following  the date on which the
telecopied  Conversion Notice has been transmitted to the Company.  Each date on
which a  Conversion  Notice is  telecopied  to and  received  by the  Company in
accordance with the provisions of this Section 3.2 shall constitute a Conversion
Date.  The Company shall convert the Debenture and issue the Common Stock Issued
at Conversion  effective as of the Conversion  Date. The Conversion  Notice also
shall state the name or names (with  addresses) of the persons who are to become
the holders of the Common Stock Issued at  Conversion  in  connection  with such
conversion.  Upon surrender for conversion,  this Debenture shall be accompanied
by a proper  assignment  hereof to the  Company  or be  endorsed  in  blank.  As
promptly  as  practicable  after the  receipt of the  Conversion  Notice and the
surrender of this  Debenture as  aforesaid,  but in any event not more than five
Business  Days  after  the  Company's  receipt  of such  Conversion  Notice  and
surrender of this Debenture, the Company shall (i) issue the Common Stock Issued
at Conversion in accordance with the provisions of this Article 3, and (ii) mail
for  delivery  by  overnight   courier  to  the  Holder  (X)  a  certificate  or
certificate(s)  representing  the number of Common Shares to which the Holder is
entitled by virtue of such conversion,  (Y) cash, as provided in Section 3.4, in
respect of any fraction of a Share issuable upon such conversion and (Z) cash in
the  amount of accrued  and unpaid  interest  as of the  Conversion  Date to the
extent payable in cash. Such conversion shall be deemed to have been effected at
the time at which the  Conversion  Notice  indicates  so long as this  Debenture
shall have been  surrendered  as  aforesaid  at such time,  and at such time the
rights of the Holder of this Debenture,  as such, shall cease and the Person and
Persons in whose name or names the Common  Stock Issued at  Conversion  shall be
issuable  shall be deemed to have  become the holder or holders of record of the
Common Shares  represented  thereby.  The Conversion  Notice shall  constitute a
contract between the Holder and the Company,  whereby the Holder shall be deemed
to  subscribe  for the  number of Common  Shares  which it will be  entitled  to
receive  upon  such  conversion  and,  in  payment  and   satisfaction  of  such
subscription  (and for any cash  adjustment to which it is entitled  pursuant to
Section  3.4), to surrender  this  Debenture and to release the Company from all
liability thereon. No cash payment aggregating less than $1.50 shall be required
to be given unless specifically requested by the Holder.

          (b) If, at any time  after  the date of this  Debenture,  the  Company
challenges,  disputes  or denies  the right of the  Holder  hereof to effect the
conversion  of this  Debenture  into Common  Shares or  otherwise  dishonors  or
rejects any Conversion  Notice  delivered in accordance with this Section 3.2 or
if at any time after the date of this  Debenture,  any third party commences any

                                        8

<PAGE>

lawsuit or proceeding or otherwise  asserts any claim before any court or public
or governmental authority which seeks to challenge, deny, enjoin, limit, modify,
delay or dispute the right of the Holder hereof to effect the conversion of this
Debenture into Common Shares,  then the Holder shall have the right,  by written
notice to the Company,  to require the Company to promptly redeem this Debenture
for cash at a  redemption  price equal to 125% of the  principal  amount  hereof
together with all accrued and unpaid interest  thereon (the "Mandatory  Purchase
Amount").  Under any of the  circumstances set forth above, the Company shall be
responsible  for the payment of all costs and expenses of the Holder,  including
legal fees and  expenses,  as and when  incurred in disputing any such action or
pursuing its rights hereunder (in addition to any other rights of the Holder).

     SECTION 3.3 [This Section Reserved]

     SECTION  3.4  Fractional  Shares.  No  fractional  Common  Shares  or scrip
representing  fractional  Common Shares shall be issued upon  conversion of this
Debenture.  Instead of any  fractional  Common Shares which  otherwise  would be
issuable  upon  conversion  of this  Debenture,  the  Company  shall  pay a cash
adjustment in respect of such fraction in an amount equal to the same  fraction.
No cash  payment  of less than  $[1.50]  shall be  required  to be given  unless
specifically requested by the Holder.

     SECTION 3.5  Reclassification,  Consolidation,  Merger or  Mandatory  Share
Exchange. At any time while this Debenture remains outstanding and any principal
amount hereof has not been converted,  in case of any reclassification or change
of Outstanding  Common Shares issuable upon conversion of this Debenture  (other
than a change in par value, or from par value to no par value per share, or from
no par  value  per  share  to par  value  or as a  result  of a  subdivision  or
combination  of  outstanding   securities   issuable  upon  conversion  of  this
Debenture) or in case of any  consolidation,  merger or mandatory share exchange
of the  Company  with  or into  another  corporation  (other  than a  merger  or
mandatory  share  exchange  with another  corporation  in which the Company is a
continuing  corporation  and which  does not result in any  reclassification  or
change,  other than a change in par value, or from par value to no par value per
share,  or from no par  value  per  share  to par  value,  or as a  result  of a
subdivision or combination of Outstanding  Common Shares upon conversion of this
Debenture), or in the case of any sale or transfer to another corporation of the
property  of the Company as an entirety or  substantially  as an  entirety,  the
Company, or such successor, resulting or purchasing corporation, as the case may
be, shall, without payment of any additional  consideration therefor,  execute a
new Debenture providing that the Holder shall have the right to convert such new

                                        9

<PAGE>


Debenture (upon terms and conditions not less favorable to the Holder than those
in effect pursuant to this Debenture) and to receive upon such exercise, in lieu
of each Common Share theretofore issuable upon conversion of this Debenture, the
kind and  amount  of  shares  of  stock,  other  securities,  money or  property
receivable upon such reclassification,  change, consolidation, merger, mandatory
share exchange, sale or transfer by the holder of one Common Share issuable upon
conversion of this Debenture had this Debenture been converted immediately prior
to  such  reclassification,   change,  consolidation,  merger,  mandatory  share
exchange or sale or transfer. The provisions of this Section 3.5 shall similarly
apply  to  successive  reclassifications,   changes,  consolidations,   mergers,
mandatory share exchanges and sales and transfers.

     SECTION 3.6 Adjustments to Conversion  Ratio. For so long as this Debenture
is  outstanding,  if the Company (i) issues and sells  pursuant to an  exemption
from registration under the Securities Act (A) Common Shares at a purchase price
representing  a percentage  of the Current  Market Price on the date of issuance
thereof that is lower than 75%,  (B) warrants or options with an exercise  price
representing a percentage of the Current Market Price on the date of issuance of
the  warrants  or  options  that is lower  than 75%,  except  for  stock  option
agreements or stock incentive  agreements,  or (C) convertible,  exchangeable or
exercisable securities with a right to exchange at lower than 75% of the Current
Market  Price on the Common  Shares on the date of  issuance or  conversion,  as
applicable, of such convertible,  exchangeable or exercisable securities, except
for stock option agreements or stock incentive  agreements;  and (ii) grants the
right to the purchaser(s)  thereof to demand that the Company register under the
Securities  Act such Common  Shares  issued or the Common  Shares for which such
warrants  or options  may be  exercised  or such  convertible,  exchangeable  or
exercisable  securities  may be  converted,  exercised  or  exchanged,  then the
Conversion  Ratio  shall  be  reduced  to equal  the  lowest  of any such  lower
percentages.

     SECTION 3.7 Optional Redemption Under Certain Circumstances. If, for two or
more Trading Days in any five-Trading  Day period (whether or not  consecutive),
the Market  Price per Common Share is less than $1.50,  then the  Company,  upon
notice  delivered  to the Holder as  provided  in Section  3.8,  may redeem this
Debenture (but only with respect to such principal amount as to which the Holder
has not  theretofore  furnished a Conversion  Notice),  at 125% of the principal
amount  thereof,  together with all accrued and unpaid  interest  thereon to the
date of redemption (the  "Redemption  Date") which shall be no later than thirty
(30) days following the expiration of such  five-Trading  Day period.  Except as
set forth in this Section 3.7, the Company shall not have the right to prepay or
redeem this Debenture.

                                       10

<PAGE>

     SECTION 3.8 Notice of Redemption. Notice of optional redemption pursuant to
Section  3.7 shall be  provided  by the  Company to the  Holder in  writing  (by
registered mail or overnight  courier at the Holder's last address  appearing in
the Company's security registry) not less than seven nor more than 15 days prior
to the Redemption Date, which notice shall specify the Redemption Date and refer
to Section 3.7  (including a statement of the Market Price per Common Share) and
this Section 3.8.

     SECTION 3.9 Surrender of Debentures.  Upon any redemption of this Debenture
pursuant to Section 3.7, the Holder shall either  deliver this Debenture by hand
to the Company at its principal  executive  offices or surrender the same to the
Company at such  address by express  courier.  Payment of the  redemption  price
specified  in Section  3.7 shall be made by the  Company  to the Holder  against
receipt of this  Debenture (as provided in this Section 3.9) by wire transfer of
immediately  available  funds to such  account(s) as the Holder shall specify to
the  Company.  If  payment of such  redemption  price is not made in full by the
Redemption Date, the Holder shall again have the right to convert this Debenture
as provided in Article 3 hereof.


                                    ARTICLE 4
                        STATUS; RESTRICTIONS ON TRANSFER

     SECTION 4.1 Status of Debenture. This Debenture is a general, unsecured and
unconditional  obligation of the Company,  and  constitutes  a legal,  valid and
binding  obligation of the Company,  enforceable  in  accordance  with its terms
subject, as to enforceability, to general principles of equity and to principles
of  bankruptcy,  insolvency,  reorganization  and other  similar laws of general
applicability relating to or affecting creditors' rights and remedies generally.

     SECTION 4.2 Restrictions on Transfer. This Debenture, and any Common Shares
issuable  according  to the terms  hereof,  have not been  registered  under the
Securities  Act. This Debenture and any Common Shares issued upon conversion may
not be offered or sold, directly or indirectly,  except pursuant to an effective
registration  statement  under the Act, or pursuant  to an  available  exemption
therefrom.


                                       11

<PAGE>
                                    ARTICLE 5
                                    COVENANTS

     The Company  covenants and agrees that so long as this  Debenture  shall be
outstanding:

     SECTION 5.1 Conversion. The Company shall not later than five Business Days
after its receipt of the Conversion Notice,  issue and deliver to the Holder the
requisite  shares of common stock  issuable  upon  conversion,  according to the
terms hereof.

     SECTION  5.2  Notice of  Default.  If any one or more  events  occur  which
constitute or which,  with notice,  lapse of time, or both,  would constitute an
Event of Default, or if the Holder shall demand the issuance of Common Shares or
take any  other  action  permitted  upon  the  occurrence  of any such  Event of
Default,  the Company shall forthwith give notice to the Holder,  specifying the
nature and status of the Event of  Default or other  event or of such  demand or
action, as the case may be.

     SECTION 5.3  Insurance.  The Company shall carry and maintain in full force
and effect at all times with insurers that are  financially  sound and reputable
such insurance in such amounts as is customary in the  respective  industries of
the Company and such subsidiaries.

     SECTION  5.4  Payment of  Obligations.  Prior to  conversion  of the entire
principal amount of this Debenture,  the Company shall pay, extend, or discharge
at or before maturity,  all its respective material obligations and liabilities,
including,  without  limitation,  tax liabilities,  except where the same may be
contested in good faith by appropriate proceedings.

     SECTION  5.5  Compliance  with Laws.  The  Company  shall  comply  with all
applicable   laws,   ordinances,   rules,   regulations,   and  requirements  of
governmental authorities.

     SECTION 5.6  Inspection of Property,  Books and Records.  The Company shall
keep proper books of record and account in which full,  true and correct entries
shall be made of all dealings and  transactions  in relation to its business and
activities  and shall  permit  representatives  of the  Holder  at the  Holder's
expense to visit and inspect any of its  respective  properties,  to examine and
make abstracts  from any of its respective  books and records and to discuss its
respective  affairs,   finances  and  accounts  with  its  respective  officers,
employees and independent public  accountants,  all at such reasonable times and
as often as may reasonably be desired.


                                       12

<PAGE>
                                    ARTICLE 6
                                    REMEDIES

     SECTION 6.1 Events of  Default.  "Event of  Default"  wherever  used herein
means any one of the following events:

          (a) the  Company  shall  default  in the  payment of  principal  of or
interest on this Debenture as and when the same shall be due and payable and, in
the case of an interest  payment  default,  such default shall continue for five
Business Days after the date such interest payment was due, or the Company shall
fail to perform or  observe  any other  covenant,  agreement,  term,  provision,
undertaking  or  commitment  under  this  Debenture,   the  Securities  Purchase
Agreement or the  Registration  Rights Agreement and such default shall continue
for a period of five  Business Days after the delivery to the Company of written
notice that the Company is in default hereunder; or

          (b) any of the  representations  or  warranties  made  by the  Company
herein, the Securities Purchase Agreement,  the Registration Rights Agreement or
in any  certificate  or  financial or other  written  statements  heretofore  or
hereafter  furnished  by or on  behalf of the  Company  in  connection  with the
execution and delivery of this Debenture,  the Securities  Purchase Agreement or
the  Registration  Rights Agreement shall be false or misleading in any material
respect on the Closing Date; or

          (c) the entry of a decree or order by a court having  jurisdiction  in
the premises adjudging the Company or any subsidiary a bankrupt or insolvent, or
approving  as properly  filed a petition  seeking  reorganization,  arrangement,
adjustment  or  composition  of or in  respect of the  Company  under the United
States Bankruptcy Code of 1978, as amended (the "Bankruptcy Code"), or any other
applicable Federal or state law, or appointing a receiver, liquidator, assignee,
trustee or  sequestrator  (or other  similar  official) of the Company or of any
substantial  part of its property,  or ordering the winding-up or liquidation of
its  affairs,  and any such decree or order  continues  and is  unstayed  and in
effect for a period of 60 calendar days; or

          (d) the institution by the Company or any Subsidiary of proceedings to
be adjudicated a bankrupt or insolvent,  or the consent by it to the institution
of  bankruptcy or  insolvency  proceedings  against it, or the filing by it of a
petition  or answer  or  consent  seeking  reorganization  or  relief  under the
Bankruptcy Code or any other applicable  federal or state law, or the consent by
it to the  filing of any such  petition  or to the  appointment  of a  receiver,
liquidator, assignee, trustee or sequestrator (or other similar official) of the
Company or of any  substantial  part of its property,  or the making by it of an

                                       13

<PAGE>

assignment  for the benefit of  creditors,  or the admission by it in writing of
its  inability  to pay its debts  generally  as and when they become due, or the
taking of corporate action by the Company in furtherance of any such action; or

          (e) a final judgment or final judgments for the payment of money shall
have been entered by any court or courts of competent  jurisdiction  against the
Company and remains  undischarged  for a period (during which execution shall be
effectively  stayed) of 30 days,  provided that the aggregate amount of all such
judgments  at any time  outstanding  (to the extent  not paid or to be paid,  as
evidenced by a written communication to that effect from the applicable insurer,
by insurance) exceeds $100,000; or

          (f) it becomes  unlawful for the Company to perform or comply with its
obligations  under this  Debenture,  the  Securities  Purchase  Agreement or the
Registration Rights Agreement; or

          (g) the  Common  Shares  shall  be  delisted  from  the  NASDAQ  Small
Capitalization Market System or suspended from trading thereon, and shall not be
reinstated,  relisted or such suspension lifted, as the case may be, within five
(5) days; or

          (h) the Company shall default  (giving effect to any applicable  grace
period)  in the  payment of  principal  or  interest  as and when the same shall
become  due  and  payable,  under  any  indebtedness,  individually  or  in  the
aggregate, of more than $100,000.

     SECTION 6.2 Acceleration of Maturity; Rescission and Annulment. If an Event
of Default occurs and is continuing,  then and in every such case any Holder may
rescind the  Conversion  Notice and obtain  payment  for the entire  outstanding
principal  amount of the  Debenture  which remains  unconverted,  by a notice in
writing to the  Company,  and upon any such  declaration  the  entire  principal
amount of this Debenture  shall become  immediately due and payable by virtue of
such  rescission;  provided,  however,  in the  case  of any  Event  of  Default
described  in  paragraphs  (c),  (d) or (f) above,  the entire then  outstanding
principal  amount  of this  Debenture,  together  with all  accrued  and  unpaid
interest thereon, automatically shall become immediately due and payable without
the necessity of any notice or declaration as aforesaid.

     SECTION 6.3 Default  Interest  Rate. (a) If any portion of the principal of
or interest on the  Debenture  shall not be paid when due (whether at the stated
maturity, by acceleration or otherwise) such principal of and interest on the

                                       14

<PAGE>

Debenture  which is due and  owing  but not paid  shall,  without  limiting  the
Holder's rights under this Debenture, bear interest at the Default Interest Rate
until paid in full.

          (b)  Notwithstanding  anything herein to the contrary,  if at any time
the  applicable  interest  rate as provided  for herein shall exceed the maximum
lawful  rate which may be  contracted  for,  charged,  taken or  received by the
Lender in accordance with applicable laws of the State of Colorado (the "Maximum
Rate"), the rate of interest applicable to the Debenture shall be limited to the
Maximum Rate.

     SECTION 6.4 Remedies Not Waived.  No course of dealing  between the Company
and the Holder or any delay in exercising any rights  hereunder shall operate as
a waiver by the Holder.

     SECTION  6.5  Waiver.  No  recourse  shall  be had for the  payment  of the
principal of, or the interest on, this Debenture, or for any claim based hereon,
or otherwise in respect hereof, against any incorporator,  shareholder,  officer
or director,  as such, past,  present or future, of the Company or any successor
corporation,  whether by virtue of any constitution,  statute or rule of law, or
by the enforcement of any assessment or penalty or otherwise, all such liability
being, by the acceptance  hereof and as part of the  consideration for the issue
hereof, expressly waived and released.

                                    ARTICLE 7
                                  MISCELLANEOUS

     SECTION 7.1 Notice of Certain Events.  In the case of the occurrence of any
event described in Sections 3.1, 3.5 or 3.6 of this Debenture, the Company shall
cause to be mailed to the  Holder of this  Debenture  at its last  address as it
appears  in the  Company's  security  registry,  at least  20 days  prior to the
applicable record,  effective or expiration date hereinafter specified, a notice
stating  (x) the date on which a record is to be taken for the  purpose  of such
dividend, distribution,  issuance or granting of rights, options or warrants, or
if a record is not to be taken,  the date as of which the  holders  of record of
Common Stock to be entitled to such dividend, distribution, issuance or granting
of rights,  options or warrants  are to be  determined  or (y) the date on which
such  reclassification,  consolidation,  merger,  sale,  transfer,  dissolution,
liquidation  or winding-up is expected to become  effective,  and the date as of
which it is expected  that holders of record of Common Stock will be entitled to
exchange their shares for securities,  cash or other property  deliverable  upon
such  reclassification,   consolidation,  merger,  sale  transfer,  dissolution,
liquidation or winding-up.

                                       15

<PAGE>

     SECTION 7.2 Register.  (a) The Company shall keep at its principal office a
register  in which  the  Company  shall  provide  for the  registration  of this
Debenture.  Upon any transfer of this Debenture in accordance with Article 2 and
4 hereof, the Company shall register such transfer on the Debenture register.

          (b) The Company may deem the person in whose name this Debenture shall
be registered upon the registry books of the Company to be, and may treat it as,
the absolute  owner of this Debenture  (whether or not this  Debenture  shall be
overdue)  for the purpose of  receiving  payment of interest on or  principal of
this Debenture, for the conversion of this Debenture and for all other purposes,
and the Company  shall not be affected by any notice to the  contrary.  All such
payments  and such  conversions  shall be valid and  effective  to  satisfy  and
discharge the liability  upon this Debenture to the extent of the sum or sums so
paid or the conversion or conversions so made.

     SECTION 7.3  Withholding.  To the extent  required by  applicable  law, the
Company may withhold amounts for or on account of any taxes imposed or levied by
or on behalf of any taxing  authority in the United States  having  jurisdiction
over the Company from any payments made pursuant to this Debenture.

     SECTION  7.4  Governing  Law.  THIS  DEBENTURE  SHALL BE  GOVERNED  BY, AND
CONSTRUED IN ACCORDANCE  WITH, THE LAWS OF THE STATE OF NEW YORK (WITHOUT GIVING
EFFECT TO CONFLICTS  OF LAWS  PRINCIPLES).  WITH RESPECT TO ANY SUIT,  ACTION OR
PROCEEDINGS  RELATING TO THIS DEBENTURE,  THE COMPANY IRREVOCABLY SUBMITS TO THE
EXCLUSIVE  JURISDICTION  OF THE  COURTS OF THE STATE OF NEW YORK AND THE  UNITED
STATES  DISTRICT  COURT  LOCATED IN THE BOROUGH OF  MANHATTAN IN THE CITY OF NEW
YORK AND HEREBY WAIVES,  TO THE FULLEST EXTENT  PERMITTED BY APPLICABLE LAW, ANY
CLAIM  THAT  ANY  SUCH  SUIT,  ACTION  OR  PROCEEDING  HAS  BEEN  BROUGHT  IN AN
INCONVENIENT  FORUM.  SUBJECT TO APPLICABLE  LAW, THE COMPANY  AGREES THAT FINAL
JUDGMENT AGAINST IT IN ANY LEGAL ACTION OR PROCEEDING ARISING OUT OF OR RELATING
TO  THIS  DEBENTURE  SHALL  BE  CONCLUSIVE  AND  MAY BE  ENFORCED  IN ANY  OTHER
JURISDICTION  WITHIN OR OUTSIDE  THE UNITED  STATES BY SUIT ON THE  JUDGMENT,  A
CERTIFIED COPY OF WHICH JUDGMENT  SHALL BE CONCLUSIVE  EVIDENCE  THEREOF AND THE
AMOUNT OF ITS INDEBTEDNESS, OR BY SUCH OTHER MEANS PROVIDED BY LAW.


                                       16

<PAGE>

     SECTION 7.5  Headings.  The  headings of the  Articles and Sections of this
Debenture are inserted for convenience only and do not constitute a part of this
Debenture.


                                       17

<PAGE>

     IN WITNESS  WHEREOF,  the Company has caused this Debenture to be signed by
its duly  authorized  officer  under its  corporate  seal,  attested by its duly
authorized officer, on the date of this Debenture.

                                      EARTH SCIENCES, INC.



                                       By:
                                           ------------------------------------
                                           Name: Mark H. McKinnies
                                            Title: President


                                      Attest


                                       By:
                                          -------------------------------------
                                               Name:  Duane N. Bloom
                                               Title:  Secretary



INITIAL
HOLDER







By:
    --------------------------
Name:
Title:

                                       18

<PAGE>



                                                                         ANNEX I




                           [FORM OF CONVERSION NOTICE]


TO:      Earth Sciences, Inc.
         910 12th Street
         Golden, Colorado 80101
         Attention:
                   -------------------------

     The undersigned  owner of this 4% Convertible  Debenture due March 31, 1999
issued by Earth Sciences,  Inc. (the "Debenture")  hereby irrevocably  exercises
its option to convert $  principal  amount of the  Debenture  into shares of the
common stock,  $.01 par value,  of Earth Sciences,  Inc.  ("Common  Stock"),  in
accordance with the terms of the Debenture. The undersigned hereby instructs the
Company to convert the portion of the Debenture  specified  above into Shares of
Common Stock Issued at Conversion in accordance with the provisions of Article 3
of the  Debenture.  The  undersigned  directs that the Common Stock issuable and
certificates therefor deliverable upon conversion,  the Debenture recertificated
in the principal amount,  if any, not being  surrendered for conversion  hereby,
together with any check in payment for fractional Common Stock, be issued in the
name of and  delivered  to the  undersigned  unless  a  different  name has been
indicated  below.  All  capitalized  terms used and not defined  herein have the
respective meanings assigned to them in the Debenture.


Dated:
       --------------------------------------

                                                 Signature
----------------------------------------------


                     Fill in for registration of Debenture:


Please print name and address
(including zip code number) :


--------------------------------------------------------------------------------

--------------------------------------------------------------------------------

--------------------------------------------------------------------------------





                                       19